Display devices with changing images have been used for many years, some on small, handheld devices, others on desktop-sized displays, for example as toys and educational displays. Medium size varying image displays are used as indoor advertisements, and large displays are used for outdoor street signs. An exemplary type of changing image outdoor display is constructed of triangular prisms. The triangular prisms are arranged so that all the prisms simultaneously present a set of facets to the view of the public. After a predetermined display period, all the prisms turn simultaneously to display the next set of facets. Since triangular prisms have three facets, such displays have three pictures, which are displayed in sequence. Each of the pictures to be displayed is divided into a plurality of linear segments, and each segment is pasted on a single facet. Typically, a plurality of segments are printed on one sheet which is pasted on a plurality of adjacent prisms, with a cut between the prisms being made after the pasting step.
Another type of multi-picture display, which is not limited to three different pictures, is based on a different principle. All the segments of all the pictures are arranged on a single indicia in a special spatial configuration. To display the images of a series of N pictures, each of the N pictures are segmented into M strips. The strips are deposited or otherwise created on a “indicia carrier”. The composite of all the strips is the indicia. In the indicia all the strips are parallel to one another. The indicia carrier may be made of any appropriate material which is of stable dimensions.
The indicia is viewed through an array of parallel cylindrical lenses. The cylindrical lens array is so designed that the distance between the focal points (lines) of the component lenses is equal to the width of the lenses and each lens views one strip. The indicia is oriented so that the strip centers are parallel to the focal lines of the cylindrical lenses of the array.
A property of this configuration is that the segments have an equal width and the centers of the segments of one picture are offset by a fixed linear amount from centers of the segments of a second picture.
The image displayed is of that picture whose linear segments (strips) are centered along the focal lines of the cylindrical lenses. By shifting the lens array (or indicia), in a direction perpendicular to the segments, by the fixed linear amount, a different picture is selectively displayed. This technique is described, for example, in U.S. Pat. No. 1,475,430, issued Nov. 27, 1923, and more recently in Japanese Patent HEI 2-211437 published Aug. 22, 1990. A recent method for the manufacture of an indicia has been described in U.S. Pat. No. 5,100,330 issued Mar. 31, 1992. All of the above patent publications are incorporated herein by reference.
The practical application of the lens array type of display has apparently been limited to small displays, such as toys, educational displays, indoor displays and the like, with measurements generally under 0.5 square meter.
The presentation using indicia carriers typically demands accuracy, particularly in the dimensional relationship of indicia parameters and the pitch of the array of lenses. While such accuracy is definitely achievable with small display units, the difficulty in achieving such accuracy may be the reason for lack of practical large lens displays.